Fifth Edition Fragility

Not that the rules are fragile; rather, rules for fragile things.
At the same time, we’ll get rules for low-quality manufacture, because that’s a great way to model it: breakable. I don’t want my PCs to be wandering pants salesmen, and making inferior shoddy goods breakable creates a real ongoing reason for them to be valueless.

First, check out the DMG page 246 (oh yes, I canceled my preorder and supported local shops. Woo!). There’s a table of object armor classes by material, a similar version of which has appeared in each edition, here presented appropriately to this setting:
Cloth, paper, rope: d2
Crystal, glass, ice: d4
Wood, bone: d6
Stone: d8
Iron, steel: d10
Mithral: d12
Adamantine: d20

Objects can be either durable or resilient, resilient objects having extra hit dice, based on size.

There’s a throwaway line about damage thresholds, needing enough damage in a single blow to stick, but no guidance. Not gonna use that here.

So here’s how a computer would model it: it would make continuous attacks against all items, forever, and track their hit points.
That seems like a pain to me. Instead, we’ll track “mishaps” and try to make them rare but meaningful, and long term wear-and-tear.

The DM declares a mishap. The DM declares which materials are affected.

During a mishap, each fragile item a character is carrying might break. For each at-risk fragile item, the player rolls the appropriate types of dice from the above table. Each rolled 1 causes a players chosen item to degrade 1 die step, breaking if it is already a d4 or lower.
Not all mishaps trigger all fragile materials; a fireball might only trigger volatile materials (which an organized DM would inform the players to mark ahead of time, fire being a frequent hazard).
Resolve all items of a given fragility together; any failures may be assigned as the player desires amongst their goods.
Stowed fragile items are considered their container, thus likely not fragile.
We’ll assume a mishap never harms a non-fragile object, because the damage just doesn’t accumulate.

During a long rest, a character must maintain their gear. If they do not, they risk it becoming fragile, thus breaking at an inopportune moment.
The cost to maintain gear is 1gp and 1 downtime day (followers may be required for certain very expensive layouts!) per 100gp of gear. Certain gear, such as silk robes, may be “finnicky” and consume 5x the usual maintenance resources.
Each piece of gear not completely cared for is at risk.
Roll a mishap check, as above; if failed, the good is now fragile. Repairing it will cost 50% of the value of the gear and the same amount of time, if that’s even possible!
PCs can have town NPCs manage their upkeep at a rate of 2gp per hireling, each of whom can handle 100gp of goods/day.
The time (or else mishap rolls) must be handled before the long rest is completed. Obviously the character can sleep during this period; resuming adventuring with the uncared for gear is what puts it at risk.

So, shoddy goods. Shoddy goods start with a lower die, or are already fragile, or both. Tadaa! Nobody wants that continuous suck on their resources!

Analysis: a long rest costs a steady gp trickle. I might need to tune the amount. It’s good for marking fragile objects as fragile and then having them break in the field. It’s a little open to fiat — tying fragile checks to short rests, dropping to 0hp or similar would be less judgmenty, but I am torn 🙂
Hurts characters with bandoliers of oil a lot, but that’s always seemed a little foolhardy to me.

Addendum: After sleeping on it, the additional “durability” of harder materials for fragile objects isn’t really useful. Ditch the complex dice, and instead, the DM should use the hardness table as a guide for which objects are at risk and the player should just roll 1d6 for each fragile at risk object, breaking the object on a 1. If the DM isn’t sure what’s at risk, they can roll an attack at +0 against the table, modifying materials up or down a few steps based on attack type.

One of the benefits of unifying this is it makes it possible for the player to batch rolls, allowing 1 die to decide all of their potions, say.

Shoddy gear should just cost more to maintain or begin as fragile, maybe be easier to fail the maintenance check during a long rest, which should be an attack against the object’s hardness.